Method of calcining and desulfurizing carbonaceous contiguous bed of agglomerates with particulate heat carriers

ABSTRACT

An improved process for calcination of agglomerates to produce coke suitable for use in ore reduction furnaces, wherein calcination is effected simultaneously in at least two different heat transfer zones, in one of which gas is the principal source of heat and in the other of which solids are the principal source of heat. A stream of hot finely divided solid heat carriers are showered downwardly through the interstices of said downwardly moving bed consisting essentially of a column of contiguous, preheated agglomerates in the calcining zone at a velocity which is greater than that of said downwardly moving bed, the temperature of said heat carrier being higher than that of said agglomerates.

United States Patent Gorin [4 1 June 20, 1972 [54] METHOD OF CALCININGAND DESULFURIZING CARBONACEOUS CONTIGUOUS BED OF AGGLOMERATES WITHPARTICULATE HEAT CARRIERS [21] Appl. No.: 53,370

52 us. C1 ..201 12, 201 17, 201/20,

201/34, 201/6, 201/36, 201/44, 23/2099 [51] lnt.Cl ..Cl0b 49/18,C10b53/O8,Cl0b 57/12 [58] Field of Search ..20l/6,10,12,17, 20, 21-24,

[56] References Cited UNITED STATES PATENTS 3,444,048 5/1969 Schemlinget al ..20l/12 X FORMING CARBONACEOUS GREEN FORMCOKE PrimaryExaminer-Norman Yudkoff Assistant ExaminerDavid Edwards Attorney-D.Leigh Fowler, Jr. and Stanley J. Price, Jr.

[ ABSTRACT An improved process for calcination of agglomerates toproduce coke suitable for use in ore reduction furnaces, whereincalcination is effected simultaneously in at least two different heattransfer zones, in one of which gas is the principal source of heat andin the other of which solids are the principal source of heat. A streamof hot finely divided solid heat carriers are showered downwardlythrough the interstices of said downwardly moving bed consistingessentially of a column of contiguous, preheated agglomerates in thecalcining zone at a velocity which is greater than that of saiddownwardly moving bed, the temperature of said heat carrier being higherthan that of said agglomerates.

GAS l PREHEATING FEED ZONE HEAT ZONE

CALCINING ZONE SEPARATION Z0 NE CALCINED FORMCOKE PATENTEDmzo 19123,671,401

SHEET 10F 2 61:5 4 IO f CARBONACEOUS FORMING GREEN FORMCOKE PREHEATINGFEED zoN AGGLOMERATES um |s 24 HEAT REGENERATION 20 l ZONE r I CALCINING|a zoNE 2a- 2e 9 22 34 V 1 I/ A SEPARATION A ZONE /30 364 L42 COOLINGI-| 0 ;g o|z|Ne zoNE GAS 7- CALCINED. FORMCOKE INVENTOR.

EVERETT GORIN METHOD OF CALCINING AND DESULFURIZING CARBONACEOUSCONTIGUOUS BED OF AGGLOMERATES WITH PARTICULATE HEAT CARRIERS BACKGROUNDOF THE INVENTION l Field of the Invention This invention relates to aprocess for producing coke suitable for use in cupolas. blast furnacesand other ore reduction furnaces, and more particularly, to an improvedheat transfer system for calcination of carbonaceous agglomerates.

2. Description of the Prior Art Many processes are known, and some arein commercial use, for making agglomerates from carbonaceous solids andbinders of diverse kinds. Briquetting presses, rotary retorts, and otherequipment have been employed in such processes to make agglomerateswhich, upon appropriate calcination, make coke suitable for use inmetallurgical operations. The term formcoke is sometimes used todescribe agglomerates in a calcined state and is so used herein.

The strength of fonncoke must be adequate to sustain the burden of theore reduction furnace. In the case of the blast furnace. the strength ofthe formcoke should be very high to minimize formation of fine particleswhich decrease furnace burden permeability. Calcination of theagglomerates plays a critical role in producing formcoke of therequisite strength. It also serves to regulate the volatile mattercontent of the formcoke. Still further. calcination may be a factor inthe desulfurization of the agglomerates to produce a low sulfurformcoke. The particular process selected for achieving one or more ofthese objectives is also a function of the composition of the green(i.e. uncalcined) agglomerates. Some agglomerates require shock heatingto prevent grape clustering." Shock heating consists of sudden exposureof the agglomerates to a high temperature. Grape clustering is the adhesion of individual agglomerates to one another to form grape-likeclusters. Other agglomerates require carefully controlled low heatingrates, at least in certain temperature ranges. to achieve the desiredstrength of the formcoke.

Illustrative of the patents which describe processes for calcination ofgreen agglomerates are the following: U. S. Pat. No. 2.87 l .004 U. S.Pat. No. 2.924.511 U. S. Pat. No. 3.0l8.226 U. S. Pat. No. 3.05l.629 U.S. Pat. No. 3.117.064 U. 5. Pat. No. 3.384.557 U. S. Pat. No. 3,444,048U. S. Pat. No. 3.475.278 British Pat. No. 741,679. All the foregoingillustrative patents disclose various methods of transferring heat tothe green agglomerates to effect calcination. However, like the priorart generally. they do not provide a heat transfer system which isreadily adaptable to the heat requirements of the various and sundryagglomerates. while producing formcoke of the desired characteristics ina continuous commercially feasible process.

Accordingly. it is the primary object of this invention to provide animproved. continuous. commercially feasible process for calciningcarbonaceous agglomerates. A secondary object is to provide a processwherein desulfurization is also effected.

SUMMARY OF THE INVENTION The present invention is a continuous processfor transferring heat to green carbonaceous agglomerates in a novel andcommercially feasible system to effect calcination.

According to the broadest aspects of the invention. the greenagglomerates are conducted through two different heat transfer zones. inthe first of which gas is the principal source of heat and in the secondof which solids are the principal source of heat. The first heattransfer zone is essentially a preheating zone. In this preheating zone,the heat is largely supplied by the hot effluent gas from the secondheat transfer zone. The second heat transfer zone is the calcinationzone proper. In this second zone, the preheated agglomerates from thefirst zone are calcined at a temperature above l.400 F. The heat issupplied in the second zone by a stream of hot heat carrier solids.

More specifically, the transfer of heat to the agglomerates in thesecond zone, that is, the calcination zone proper. is accomplished inaccordance with my invention as follows. A downwardly moving bed of thepreheated agglomerates from the preheating zone is established andmaintained. Then a stream of the hot heat carrier solids is showereddown over the agglomerates and through the interstices of the downwardlymoving bed at a velocity which is greater than that of the bed itself.At the same time, a stream of non-oxidizing gas is circu lated upwardlythrough the bed in countercurrent flow relationship to the bed and tothe hot heat carrier solids. The latter supply the heat required tocalcine the agglomerates either by direct transfer to the agglomeratesor by transfer to the gas and thence to the agglomerates. The stream ofupflowing gas aids in maintaining uniformity of heat transfer throughoutthe bed of agglomerates by reason of its dispersal of the downwardlyshowering heat carrier. In the process. its own temperature is raised tothe point where it can serve as the preheating gas used in the firstheat transfer zone.

The agglomerates are maintained in the calcination zone long enough toproduce the desired calcination. Then the heat carrier solids areseparated and recycled after appropriate regeneration which simplyconsists of reheating if the heat carrier is an inert solid such assand. However, the heat carrier may be an H 5 acceptor such as manganeseoxide. By use of such an acceptor as a heat carrier, desulfurization maybe concurrently effected in the case of agglomerates derived from asulfur-containing coal. In the calcination of such hydrocarbonaceoussolids, some hydrogen is evolved which reacts with the sulfur to form H8. The acceptor reacts with the H 8 to form the sulfide. The latter maybe regenerated in any suitable manner, as well as reheated. beforerecycle to the calcination zone. Accordingly, as used herein, the termregeneration" means reheating and restoring the heat carrier to itseffective state for reuse in the calcination zone.

In accordance with the preferred embodiment of the invention, theprocess is applied to hydrocarbonaceous agglomerates which require acontrolled heating rate from about l.I0O to about I,450 F. to produceformcoke of the requisite strength. In the preferred embodiment. the hoteffluent gas from the calcination zone is passed upwardly andcountercurrently through a downwardly moving bed of the agglomerates inthe preheating zone. The relative temperatures of solids and gas in thepreheating zone. as well as their respective velocities, are regulatedto maintain a heating rate which does not exceed l0 F. per minute overthe range of about I,I00 to about l,450 F. By about, I mean :50 F.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of myinvention, its objects and advantages. reference should be had to theaccompanying drawings in which FIG. 1 is a schematic illustration of theprocess of my invention in its broadest aspects, and

FIG. 2 is an illustration, partly schematic and partly in cross section,of the preferred embodiment of the process of my invention.

DESCRIPTION oF FIG. 1

Referring to FIG. I of the drawings. numeral 10 designates a FormingZone in which a carbonaceous feed'is fonned into green agglomerates byany of the well-known methods for doing so. The carbonaceous feed may beeither coalor petroleum-derived. The temperature in the Forming Zone isgenerally below l,l00 F. The green agglomerates are conducted to thefirst heat transfer zone, designated as Preheating Zone and by thenumeral I2. In this zone 12, the green agglomerates are heated by a hotnon-oxidizing gas circulated in direct heat exchange relation with theagglomerates. The heatdepleted gas is discharged through a line I4.

The preheated agglomerates are conducted through a conduit 16 to thesecond heat transfer zone, the Calcining Zone designated by the numeral18, wherein the agglomerates are heated to a temperature in the range ofabout l,600 to about l800 F. at elevated pressures up to 200 psig andeven higher. A bed of the agglomerates is established in the CalciningZone which moves downwardly by gravity through the zone. A stream of hotsolids, introduced into the calcining zone by a conduit 20, is showereddown over the agglomerates and through the interstices of the moving bedof agglomerates at a velocity which is greater than that of the bed. Atthe same time, a non-oxidizing gas is introduced into the bottom of theCalcining Zone through a conduit 22 and is circulated upwardly throughthe Calcining Zone to assist in the uniform dispersal of the showeringheat carrier and in the transfer of heat to the agglomerates, while atthe same time being heated itself to a temperature sufficiently high topermit its use via conduit 24 as the heat carrier in the Preheating Zone12.

The calcined agglomerates admixed with the heat carrier solids areremoved from the Calcining Zone 18 to a Separation Zone 30. Conduits 26and 28 are really one conduit, but are shown separately for the removalof the calcined agglomerates and heat carrier to schematicallyillustrate the flow of the two different solid streams. The latter areseparated in the Separation Zone. The heat carrier is conducted to aRegeneration Zone 32 through a conduit 34 to be reheated andreactivated, as the case may be. The regenerated solids, at therequisite temperature, are recycled to the Calcining Zone via conduit20.

The separated calcined agglomerates are conducted by a conduit 36 to aCooling Zone 40 where they are cooled by direct heat exchange with thenon-oxidizing gas which is introduced into the Cooling Zone by conduit38 and discharged therefrom through conduit 42 to the Separation Zoneand thence to the Calcining Zone through conduit 22. The cooled produceCalcined Formcoke is discharged through conduit 44. ln some instances,it may be more convenient to separate the calcined agglomerates and theheat carrier after cooling rather than as shown in FIG. 1. In eithercase, however, the temperature of the product Formcoke is sufficientlyreduced by the gas to eliminate any need for water quenching which issuch an undesirable feature of present coke oven practice.

In FIG. 2 of the drawings, there is shown the preferred embodiment ofthe present invention, including the preferred method of forming thegreen agglomerates. The latter method is described in detail in U. S.Pat. No. 3,073,751 and will be described only briefly here. Coal, char(i.e. distillation residue of coal) and pitch in suitable proportionsare fed to a substantially horizontal rotary kiln 50. The coal is fed tothe kiln through a conduit 52 after being preheated by a Heater 54. Somecoal is also fed to a low temperature carbonization unit (LTC)designated by the numeral 56 where it is distilled to yield char. Thischar, together with recycled char from a conduit 58, is preheated in aChar Heater 60 from which it is fed through a conduit 62 to the kiln 50.Pitch is introduced into the kiln via a conduit 64 which is connected toa fractionating column 66 that receives tar vapors from the kiln. Thetemperatures of the feed materials to the kiln are adjusted to maintainthe desired forming temperature which is between about 725 and 825 F.Green agglomerates, sometimes called pellets, are formed in the kiln 50,sometimes called Pelletizer," and leave the kiln at a temperature in theindicated range. Off-size pellets are separated, crushed, (not shown)and recycled through conduit 58. The remainder of the pellets, most ofwhich are in the size range one-half inch to 3 inches, are conductedwithout deliberate cooling through a conduit 68 to the top ofa retort70.

The retort 70 is stationary, vertical, generally cylindrical vesseladapted to confine a calcining zone at high temperatures and elevatedpressures. The green pellets are introduced into the top of the retortand, as they flow downwardly through the retort, form a column (ordownwardly moving bed) of the contiguous pellets from the top to a pointnear the bottom of the retort where a grid Separator 72 is arrangedtransversely across the retort.

The upper portion of the retort serves as the preheating zone of theincoming pellets. That portion is labeled Preheater. It extends from thetop of the retort'to the point where the major part of the solid heatcarrier is introduced into the retort through a distributor 74. Thelower part of the retort houses the calcination zone which extendsdownwardly to the Separator and is labeled Calciner.

The major source of heat for the Preheater is the hot effluent gas fromthe Calciner. However, when the solid heat carrier to the Calciner is anH 8 acceptor, as it is in this preferred embodiment, then a small amountof the hot acceptor may be introduced into the top of the Preheaterthrough a distributor 76, primarily to remove the last vestiges of H 5that may still be present in the effluent gas, but at the same timesupplying a modest amount of supplemental heat. It is essential tomaintain a pellet heating rate in the preheater which is below 10 F. perminute, at least in that zone of the preheater where the pellets are ata temperature between about 1,100 and about l,450 F. The desired heatingrate is achieved by appropriate adjustment of the relative velocities ofthe downwardly moving bed of pellets and the upwardly flowing gas, aswell as the amount of acceptor which is introduced by the distributor76.

As the downwardly moving bed of preheated pellets, now at about l,450F., enters the Calciner, it is met by a shower of the hot acceptorsolids introduced through the distributor 74.' Other distributors may beprovided at lower points for injecting supplemental hot solids. Thesolids, inert or acceptor, used in the process of this invention, aregenerally finely divided with a top size usually below eight mesh(Standard Tyler screen) in order to obtain high heat transfer ratesbetween the heat carrier and the gas. The minimum size is determined bythe density of the solids and the gas upflow velocity in the Calcinerand must be such that it is not transported upwardly to any great extentabove the heat carrier solids feed point. Generally, the minimum size isabove 400 mesh but this will vary with the detailed geometrical designand the operating pressure in the Calciner.

The gas has a dual function. It aids in the uniform dispersal of theacceptor solids throughout the bed of pellets, and it acts as a heattransfer medium for transfer of heat from acceptor to the pellets. Theheight of the Calciner is such that, by the time the pellets reach theSeparator, they have been heated to a temperature within the range 1,600to l,800 F.

The calcined pellets are separated from the smaller size acceptor solidsby the grid Separator 72. The acceptor solids pass through the gridopenings while the pellets fall through standlegs 80. A plate 82,preferably inclined, through which the pipes extend, serves to limitpassage of upflowing gas to the standlegs 80. The velocity of gas ishigh enough to prevent the fine solids from flowing down the standleg;i.e. it is above the terminal velocity of the coarsest particles. Thespace below plate 82 defines a cooling zone 84, also labeled Cooler. Arelatively cool non-oxidizing gas is introduced into this cooling zoneby means of a distributor 86. This gas passes countercurrently to thepellets descending through the zone. There is a transfer of heat fromthe hot pellets to the ascending gas. The cooled pellets are withdrawnfrom the retort 70 through a conduit 88 as Calcined Formcoke, thedesired product.

The non-oxidizing gas introduced into the Cooler serves many purposes.After leaving the Cooler, it assists in the separation of the acceptorsolids from the pellets as above described. When it passes through thegrid Separator 72, it is dispersed uniformly throughout the downwardlymoving streams of solids. Its velocity is carefully regulated so as tosomewhat hinder the flow of acceptor solids as they shower downwardlythrough the interstices, but not enough to reduce the downward velocityof the acceptor to that of the pellets. There is a devolatilization ofthe pellets as their temperature rises. The evolved vapors include tarvapors, hydrogen, methane and H 5. The H 8 is largely absorbed by theacceptor, converting it to its sulfide form. The vapors ascend with thenon-oxidizing gas which is heated to a temperature approaching that ofthe acceptor solids by the time the effluent gas and vapors reach thedistributor 74. The resulting hot gas, as previously stated, serves asthe principal heat source in the Preheater. Any residual H 8 is pickedup by the acceptor solids introduced through the distributor 76. The nowpartially cooled gas and effluent vapors are discharged from the top ofthe retort 70 through a conduit 90. A side stream is recycled through aconduit 92 for reuse as nomoxidizing gas after appropriate clean-up in aScrubber 94.

The separated acceptor solids leave the retort 70 through a conduit 96and are conveyed to a Regenerator 98. The acceptor solids are metaloxides which, upon reaction with H 8, form the corresponding sulfides.Their use as H 8 acceptors, as well as their regeneration, is fullydescribed in U. S. Pat. No. 2,824,047. The regeneration is generallyeffected by passing air through a fluidized bed of the acceptor. Thereis always some carry-over of carbonaceous solids with the acceptorsolids. The air burns the carbon to heat up the bed, and the oxygen alsoreacts with the sulfide to convert it to the oxide. The temperature ofthe bed of acceptor may be regulated to fall within the desired range of1,700 to 1950 F. The regenerated acceptor is then transported byconduits 100 and 102 to the retort 70 to serve as previously described.

EXAMPLES The following Table presents a summary of conditions andresults obtained in two runs made at low pressure (25 psia) employingsand and manganese oxide (Mno), respectively, as heat carriers. Thegreen agglomerates consisted of pellets made in a rotary kiln from ahighly caking Pittsburgh Seam bituminous coal, as described inconnection with FIG. 2, from a mixture of coal and char in the relativeproportions of 47 weight percent coal and 53 weight percent char. Thesize range of the green agglomerates was three-fourth inch to 2 inchesdiameter. The size range of the heat carrier (sand or oxide) was 28 to100 mesh (Tyler Standard).

The high nitrogen content of the make gas arises from the use ofnitrogen purge gas in the particular equipment used. It does not,therefore represent the true composition of the make gas whichordinarily will contain only about 1.5 volume percent nitrogen.

The high heat carrier/coke ratio used does not represent commercialoperation where it would be much lower, usually about one. The highratio in this instance was necessitated in order to make up for largeheat losses incidental to the relatively small scale equipment employed.

TABLE Conditions Run A (sand) Run B (MnO) Inlet temperature, heatcarrier, F 1,720 1,750 Ratio of heat carrier/green coke 3. 8 5. 4 Temp.profile in retort:

Preheater (range, F.) 7401,476 7501,445 Calciner (range, F.).1,475-1,662 l,446-1,665 Cooler (range, F.) 1, 507-476 1, 510-376 Max.heating rate in critical heating Zone, F./min 5.7 Calcined formcokewithdrawal rate,

1b./hr 51 48 Heat carrier withdrawal rate, lb./hr 234 298 Non-oxidizingfeed gas flow rate,

s.e.f.h 470 700 N on-oxidizing feed gas velocity, ft./sec 1. 2 1. 8Composition of exit gas, Vol. percent:

19. 75 25. 53 55. 66 52. 39 16. 07 12. 20 7. 40 8. 90 0. 45 0. 64 0. 5O0. 84 O 0.08 0. 07 Cnlclned coke evaluation:

ASTM stability 60. 5 46. 0 ASIM hradness 70. 4 58. 9 Average percent Srejected 31. 3 61. 7

According to the provisions of the patent statutes, 1 have explained theprinciple, preferred construction and mode of operation of my inventionan have illustrated and described what I now consider to represent itsbest embodiment. However, i desire to have it understood that, withinthe scope of the appended claims, the invention may be practicedotherwise than as specifically illustrated.

I claim:

1. The method of converting carbonaceous agglomerates to formcokesuitable for use in an ore reduction furnace which comprises:

a. passing said carbonaceous agglomerates through a preheating zone indirect heat exchange relation with a nonoxidizing gas which is at ahigher temperature than the ag glomerates,

b. establishing and maintaining a downwardly moving bed consistingessentially of a column of contiguous preheated agglomerates in acalcining zone.

. showering a stream of hot finely divided solid heat carrier downwardlythrough the interstices of said downwardly moving bed of agglomerates insaid calcining zone at a velocity which is greater than that of saiddovmwardl moving bed, the temperature of said heat carrier being higherthan that of said agglomerates,

passing a non-oxidizing gas upwardly through said calcining zone incountercurrent flow relationship with both downwardly moving streams ofsolids,

. regulating the transfer of heat from said heat carrier to saidagglomerates to raise the temperature of said agglomerates above 1,400F. while they are maintained in said calcining zone until the desiredcalcination is effected,

conducting the efiluent gas from the calcining zone to the preheatingzone to serve as the non-oxidizing gas in step separating the solid heatcarrier from the calcined agglomerates, and

h. recovering the calcined agglomerates.

2. The method of converting carbonaceous agglomerates to formcokesuitable for use in an ore reduction furnace which comprises:

a. passing said carbonaceous agglomerates through a preheating zone indirect heat exchange relation with a nonoxidizing gas which is at ahigher temperature than the agglomerates,

. regulating the rate of heat transfer from the non-oxidizing gas tosaid agglomerates in said preheating zone so that the temperature ofsaid agglomerates is raised at a rate less than 10 F. per minute overthe temperature range of about l,l00 to about l,450 F.,

c. establishing and maintaining a downwardly moving bed consistingessentially of a column of contiguous preheated agglomerates from step(b) in a calcining zone,

. showering a stream of hot finely divided solid heat carrier downwardlythrough the interstices of said downwardly moving bed of agglomerates insaid calcining zone at a velocity which is greater than that of saiddownwardly moving bed, the temperature of said heat carrier being higherthan that of said agglomerates,

e. passing a non-oxidizing gas upwardly through said calcining zone incountercurrent flow relationship with both downwardly moving streams ofsolids,

regulating the transfer of heat from said heat carrier to saidagglomerates to raise the temperature of said agglomerates above 1,400F. while they are maintained in said calcining zone until the desiredcalcination is effected,

g. conducting the effluent gas from the calcining zone to the preheatingzone to serve as the non-oxidizing gas in step h. separating the solidheat carrier from the calcined agglomerates, and regenerating thecarrier for reuse in the calcining zone, and i. recovering the calcinedagglomerates. 3. The method according to claim 2 in which thecarbonaceous agglomerates are derived from sulfur-containing coal.

4. The method according to claim 3 in which the solid heat carrier is anH 8 acceptor.

5. The method according to claim 4 in which a minor portion of the H 8acceptor is introduced into the preheating zone. 5

6. in the process of making calcined formcoke pellets from asulfur-containing coal which includes the formation of the green pelletsin a rotary tumbling kiln followed by calcination of the green pelletsto produce formcoke suitable for use in an ore reduction furnace, theimprovement in the calcination step of said process which comprises:

a. establishing and maintaining a downwardly moving bed consistingessentially of a column of contiguous pellets,

b. introducing hot finely divided H 8 acceptor solids into saiddownwardly moving bed of pellets, a minor proportion of said acceptorsolids being introduced into the top of said bed while the rest isintroduced therebelow,

c. showering said hot acceptor solids downwardly through the intersticesof said downwardly moving bed of pellets at a velocity which is greaterthan that of said downwardly moving bed,

d. passing a non-oxidizing gas upwardly through the downwardly movingstreams of solids in countercurrent flow relationship thereto,

e. regulating the temperature of the acceptor solids introduced into thedownwardly moving bed of pellets and the relative velocities and amountsof the gas stream and the two streams of solids to preheat the pelletsin the top portion of the downwardly moving bed to about l,450 F. at aheating rate less than 10 F. per minute over the range of about l,l00 toabout 1,450 F., and to maintain the temperature of the pellets abovel,400 F. in the lower portion of the bed until the desired calcinationis effected,

f. separating the acceptor solids from the calcined pellets,

and regenerating the acceptor solids for recycle to the downwardlymoving bed, and

g. recovering the calcined pellets as formcoke suitable for use in orereduction furnaces.

7. In the process of heat-treating heat-sensitive carbonaceousagglomerates, the improvement which comprises:

a. establishing and maintaining a downwardly moving bed consistingessentially of a column of contiguous heat-sensitive carbonaceousagglomerates in a vertical retort,

. introducing a stream of hot heat carrier solids of finer sizeseparating said heat-carrier solids from said heat-sensitive solids atthe foot of said column of downwardly moving bed of solids,

. passing gas in heat exchange relation with the now hot separatedheat-sensitive solids to effect cooling of said solids in a coolingzone,

. circulating the efiluent gas from said cooling zone upwardly incountercurrent flow relationship to both downwardly moving streams ofsolids to assist in the transfer of heat from the heat-carrier solids tothe heatsensitive solids in a heating zone while at the same time beingitself further elevated in temperature, and

, continuing the circulation of the gas beyond said point ofintroduction of heat-carrier solids upward through and in countercurrentflow relationship to the downwardly moving bed of heat-sensitive solidsto effect preheating thereof in a preheating zone.

UNITED STATES PATENT OFFICE QERTIFICATE OF CORRECTION Patent No. 3 671401 Dated June 20 1972 Inventofls) Everett Gorin It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

On the Abstract page at [7 3] Change the name of the Assignee from"Consolidated Coal Company" to e-Consolidation Coal Company; g

Col 3 line 35 "produce" should read -product;

Col 5 at the Table: Under the heading "Run B (MnO) insert the figure -47- across from the line reading "Max. heating rate in critical heatingzone F ./min.

Signed and sealed this 2 +th day of'April 1973.

(SEAL) r "ttest:

EDl a ARD l-i. FLElCHER, JR. ROBERT GOTTSCHALK Attesting OfficerCommissioner of Patents

2. The method of converting carbonaceous agglomerates to formcokesuitable for use in an ore reduction furnace which comprises: a. passingsaid carbonaceous agglomerates through a preheating zone in direct heatexchange relation with a non-oxidizing gas which is at a highertemperature than the agglomerates, b. regulating the rate of heattransfer from the non-oxidizing gas to said agglomerates in saidpreheating zone so that the temperature of said agglomerates is raisedat a rate less than 10* F. per minute over the temperature range ofabout 1,100* to about 1,450* F., c. establishing and maintaining adownwardly moving bed consisting essentially of a column of contiguoUspreheated agglomerates from step (b) in a calcining zone, d. showering astream of hot finely divided solid heat carrier downwardly through theinterstices of said downwardly moving bed of agglomerates in saidcalcining zone at a velocity which is greater than that of saiddownwardly moving bed, the temperature of said heat carrier being higherthan that of said agglomerates, e. passing a non-oxidizing gas upwardlythrough said calcining zone in countercurrent flow relationship withboth downwardly moving streams of solids, f. regulating the transfer ofheat from said heat carrier to said agglomerates to raise thetemperature of said agglomerates above 1,400* F. while they aremaintained in said calcining zone until the desired calcination iseffected, g. conducting the effluent gas from the calcining zone to thepreheating zone to serve as the non-oxidizing gas in step (a), h.separating the solid heat carrier from the calcined agglomerates, andregenerating the carrier for reuse in the calcining zone, and i.recovering the calcined agglomerates.
 3. The method according to claim 2in which the carbonaceous agglomerates are derived fromsulfur-containing coal.
 4. The method according to claim 3 in which thesolid heat carrier is an H2S acceptor.
 5. The method according to claim4 in which a minor portion of the H2S acceptor is introduced into thepreheating zone.
 6. In the process of making calcined formcoke pelletsfrom a sulfur-containing coal which includes the formation of the greenpellets in a rotary tumbling kiln followed by calcination of the greenpellets to produce formcoke suitable for use in an ore reductionfurnace, the improvement in the calcination step of said process whichcomprises: a. establishing and maintaining a downwardly moving bedconsisting essentially of a column of contiguous pellets, b. introducinghot finely divided H2S acceptor solids into said downwardly moving bedof pellets, a minor proportion of said acceptor solids being introducedinto the top of said bed while the rest is introduced therebelow, c.showering said hot acceptor solids downwardly through the interstices ofsaid downwardly moving bed of pellets at a velocity which is greaterthan that of said downwardly moving bed, d. passing a non-oxidizing gasupwardly through the downwardly moving streams of solids incountercurrent flow relationship thereto, e. regulating the temperatureof the acceptor solids introduced into the downwardly moving bed ofpellets and the relative velocities and amounts of the gas stream andthe two streams of solids to preheat the pellets in the top portion ofthe downwardly moving bed to about 1,450* F. at a heating rate less than10* F. per minute over the range of about 1,100* to about 1,450* F., andto maintain the temperature of the pellets above 1,400* F. in the lowerportion of the bed until the desired calcination is effected, f.separating the acceptor solids from the calcined pellets, andregenerating the acceptor solids for recycle to the downwardly movingbed, and g. recovering the calcined pellets as formcoke suitable for usein ore reduction furnaces.
 7. In the process of heat-treatingheat-sensitive carbonaceous agglomerates, the improvement whichcomprises: a. establishing and maintaining a downwardly moving bedconsisting essentially of a column of contiguous heat-sensitivecarbonaceous agglomerates in a vertical retort, b. introducing a streamof hot heat carrier solids of finer size consist than the heat-sensitivesolids into the downwardly moving bed of said heat-sensitive solids at apoint intermediate the top and bottom of the column of downwardly movingheat-sensitive solids, c. showering said heat-carrier solids downwardlyover the heat-sensitive solids and through the interstices thereof at ahigher velocity than that of said hEat-sensitive solids, d. separatingsaid heat-carrier solids from said heat-sensitive solids at the foot ofsaid column of downwardly moving bed of solids, e. passing gas in heatexchange relation with the now hot separated heat-sensitive solids toeffect cooling of said solids in a cooling zone, f. circulating theeffluent gas from said cooling zone upwardly in countercurrent flowrelationship to both downwardly moving streams of solids to assist inthe transfer of heat from the heat-carrier solids to the heat-sensitivesolids in a heating zone while at the same time being itself furtherelevated in temperature, and g. continuing the circulation of the gasbeyond said point of introduction of heat-carrier solids upward throughand in countercurrent flow relationship to the downwardly moving bed ofheat-sensitive solids to effect preheating thereof in a preheating zone.